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Class D Switching Power Amplifiers and Power D/A conversion

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Old 8th December 2003, 09:47 PM   #11
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Ok, I'm preparing to get 4,5 KW from my 1,5 KW toroid
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Old 8th December 2003, 09:52 PM   #12
TNT is offline TNT  Sweden
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I have now owned a pair of monoblocks based on Ice-power (semi-diy) and I think they are superior in certain areas. I would never buy anything else actually.

The trancparency and directness is stunning. Everything alse just sound dull or artificial compared.

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Old 8th December 2003, 10:23 PM   #13
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Just wanted to show you this, i placed a 500 VA to the right of the 55VA one playing.

The bottom is powder painted, so i had to use thermal grease to get a good cooling for the amplifier. Note the main caps are 2200 uF 100V. Not much to find in a 200W Amp. Just to test the sound anyway.
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Old 9th December 2003, 03:34 AM   #14
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Default Pardon the interruption, but......

Most of the amps that we are talking about are not Class D, but Class G.

And they do have distortion............

Jocko
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Old 9th December 2003, 06:47 AM   #15
FACTOR is offline FACTOR  India
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Default 2KW CLASS_D SUBWOOFER AMPLIFIER

Hello Guys Iam AbHiShEk from "InDiA"and Listen to me About my LOW COST CLASS-D PWM 2KW SUBWOOFER AUDIO AMPLIFIER
Features
1 No mains transformer needed i.e. operated directly from 220V AC mains @ 340V DC
2 Power output 2000 W RMS with lots of "SUBSONIC THUNDERBOLTS"
3 Frequency response 10Hz to 200Hz +-1dB
4 Switching Frequency @ 5KHz only "hahahahahahahaha" but too much for subsonic Class-D amp
5 Light weight Fan cooled Heatsink used because the efficiency is > 90 %
6 Dampening Factor > 500 @ 4 OHMS
7 No Feedback used ThereFore RealTime Amplification
8 THD < 0.1% @ full power
9 0 % Crossover Distortion
10 FINALLY Fully TESTED WITH 2 X 18" Low Frequency Drivers @ 8ohms 1000 W RMS each
Major Components used are SG3524 PWM Modulator/Oscillator/Error amp, OptoIsolated Gate drivers,2 X 75A IGBTs in pull manner, 8 X 550 mFD 400V Capacitors for Filtering,1000 V /35A Bridge Rectifier, 12dB/octave Linkwitz-Riley Low-Pass passive output filter and ofcourse a little bit of resistors and small capacitors etcetra.

WANNA BUILD IT YOURSELF or You Think I must be "KIDDING"
THEN MAY I HELP U PLEASE @ FACTOR_TEN@HOTMAIL.COM
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Old 9th December 2003, 08:08 AM   #16
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Lars Clausen wrote:

Quote:
Noise instead of harmonic distorsion (less disturbing to ear)
I can agree that noise is is less disturbing to the ear than distortion.
But could you be more specific ? Are you talking about PWM or delta-sigma or what else ? Could you supply measurement results ?

Regards

Charles
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Old 9th December 2003, 09:47 AM   #17
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I really don't subscribe to this eternal discussion about the ultra exact definition of classes. Just don't find it interesting. For some people it's the only interesting discussion to have...
But it seems that no two people have the same perception of what those classes really mean, so the discussion can go on and on. I know i have referred to class terms in the past, but i have decided in the future not to. (Except for class A and A/B).

My amp is a PWM (Pulse Width Modulation) amplifier, the modulator is not a Sigma Delta type, but i actually got the inspiration for it in the book 'Sigma Delta Converters' by James Candy. (Brilliant book!).

I think the Pulse Width Modulation term covers just about cover every amplifier of this type, be it digital, analog switching etc.
Even if some vendors try to confuse the customer by saying: Our technology is much better than the old crappy PWM. It's pretty much like saying:

If you eat our pill, you will only breathe clean air.

So to win the customer over, these same vendors sometimes invent all new 'classes' as 'proof' that their PWM amplifier is different from the rest. Total confusion yes.. But true product information? Not so much!

I will supply measurement results very soon. THD is around 0.02% in the range 100 - 5000 Hz, going slightly up above 5000 Hz.
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Old 9th December 2003, 10:25 AM   #18
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Lars, what about radiation?

I had some terrible experiences in the past with a Tripath evaluation board, which was inherently unstable and gave out massive amounts of RF, to the point of triggering self-oscillation!

I'm toying with the idea of building a 6-channel power amp and I'm concerned that it might give out a substantial amount of radiation, to the point of disturbing my tuner and/or other equipment.
Keeping the speaker cables short wouldn't be an option, since my equipment rack is located 3+m. away from the speakers.

How would you approach and possibly solve this problem?
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Old 9th December 2003, 10:55 AM   #19
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Hi Lars

So you are definitely talking about a classic PWM, do we agree upon this ?
In this case I'd like to know how you come to the conclusion that one does trade noise against distortion within such an amp ?
As far as I experienced do the same mechanisms that reduce distortion also reduce noise.

Regards

Charles
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Old 9th December 2003, 02:28 PM   #20
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phase_accurate: PWM stands for Pulse Width Modulation. It is the widest denominator for all amps that give out 1's and 0's.

It is unrelated to the specific mechanisms you refer to that control the signal conversion, amplification, noise THD etc. So you may say 'Classic PWM' or 'Modern PWM', it's like saying 'Classic Weather' or 'Modern Weather'. PWM is PWM. And you can put a whole bunch of 'classes' in that box ..

Different methods are usable to generate the PWM signal, and some of them don't have harmonic distortion, (since they don't have any analog audio signal processing), only a noise floor.
Of course you can also have PWM modulators that have analog signal processing and harmonic distortion. So it was not a general term. The one i use is the integrator type, with no analog signal processing, and therefore no THD.
It has distortions, but the harmonics of the distortions are random nonharmonics of the signal, (or the same as: noise).
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